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ON

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MEDULLA OBLONGATA

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MEDULLA SPINALIS.

BY

MARSHALL HALL, M.D., F.R.S. L. & E., &c. &c.

From the PHILOSOPHICAL TRANSACTIONS.

LONDON :

PKINTED BY RICHARD TAYLOR, RED LION COURT, FLEET STREET.

1833.

TO

BENJAMIN COLLINS BRODIE, Esq., F.R.S.,

SERJEANT-SURGEON TO THE KING,

Sfc. 8(C.,

TO WHOSE LABOURS

PHYSIOLOGY AND SURGERY ARE ALIKE DEEPLY INDEBTED,

THIS MEMOIR

IS INSCRIBED
BY HIS OBLIGED FRIEND,

THE AUTHOR.

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[ 635 ]

XXVI. On the Reflex Function of the Medulla Oblongata and Medulla Spi-
nalis. By Marshall Hall, M.D., F.R.S. L. 8^ E., 8^c. 8^c.

Received June 11, — Read June 20, 1833.

1. Introduction.

The his/her departments of every science are doubtless its general principles
and its laws. These have a claim to our consideration beyond that of insulated
facts or mere details. Impressed with this truth, I have hitherto devoted my
attention chiefly to the laws and principles of physiology. In a former memoir*,
I gave the outline of one of the most general of the laws of this science, — that
of the inverse ratio of the respiration and of the irritability. In the present
memoir, I propose to give an account of a principle of action in the animal
economy, which has not hitherto, I think, been distinguished with sufficient
precision from the other vital and animal functions.

The principle to which I have adverted is connected, in a peculiar manner,
with the medulla oblongata and the medulla spinalis. There is still much dis-
crepancy of opinion amongst physiologists, in regard to the properties and
functions of these parts of the nervous systeim Legallois concluded, from
his interesting series of experiments, that the spinal marrow, as a whole, and in
distinct portions, is the exclusive source of sensation and voluntary motion.
He observes-f-, “ La vie du tronc depend de la moelle 4pini^re, et celle de
chaque partie depend specialement de la portion de cette moelle dont elle
rc9oit ses nerfs. De plus, il est facile de demontrer que cette prerogative de
la moelle epiniere, d’etre la source du sentiment et de tons les mouvemens
volontaires du tronc, lui appartient exclusivement a tout autre organe.” The
Reporters of the Institute adopt the conclusions of Legallois : “ M. Legal-
lois,” they observe:};, “ a demontre que la section de la moelle epiniere sur les

* Philosophical Transactions for 1832.

t CEuvres de Legallois, Paris 1824, tome i. p. 62. J Ibid. p. 251.

MDCCCXXXIII. 4 N

636

DR. MARSHALL HALL ON THE REFLEX FUNCTION

premieres on sur les derni^res vert^bres cervicales, n’arrete que les rnouvemens
inspiratoires, et qii’elle laisse subsister dans tout le corps le sentiment et les
rnouvemens volontaires. Cette distinction est capitale : personne ne I’avait
faite avant lui*.” M. Cruveilhier, on the other hand, denounces this view of
the functions of the spinal marrow as one of the errors of modern physiology.
He observes'l', “ L’independence des diverses parties de la moelle les unes des
autres, I’independence de la moelle du cerveau, assez gen^ralement admise
dans ces derniers temps, me parait une grave erreur physiologique fond6e sur
d’ingenieuses experiences. L’opinion des anciens, qui regardaient la moelle
comme un gros cordon nerveux destine ^ repondre lui seul a tons les nerfs de
I’economie, pour transmettre en definitive au cerveau les impressions, on pour
en recevoir les impulsions volontaires ou organiques, cette opinion est bien
plus en harmonic avec les faits, avec la grande loi anatomique de la continuite
du syst^me nerveux.”

It will not be difficult to prove that the conclusions of Legallois and the
Reporters of the Institute, are not legitimate deductions from the facts before
them. But M. Cruveilhier altogether overlooks these facts, which are amongst
the most interesting in physiology, and adopts an opinion which, however true,
is far too exclusive.

On the more recent occasion of a report upon the admirable work of
M. Flourens, the Perpetual Secretary of the Institute states his opinion on this
point in a manner far more problematical. “ L’auteur,” he observes, ‘‘ conclut
(jue la sensation et la contraction n’appartiennent plus k la moelle ^pini^re
qu’aux nerfs ; et cette conclusion est certaine pour les animaux entiers. Ce
serait une grande question de savoir si elle Test ^galement pour les animaux
qui ont perdu leur encephale, et qui, dans certaines classes, paraissent loin de
perdre sur-le-champ leurs fonctions animales;):.”

* More recently, M. Magendie, M. Lallemand, and M. Ollivikr have repeated the same opinion;
Anatomie des Syst^mes Nerveux, par A. Desmoulins, Paris 1825, p. 561,&c.; Obser\-ations Patholo-
giques propres it ^clairer la Physiologie, ed. 2, Paris 1825, pp. 88, 96, &c.; Traits de la Moelle Epinibre,
ed. 2, Paris 1827, p. 17, &c. The subject is unnoticed by M. Serres: Anatomie Compar6e du Cerveau,
Paris 1824. The physiologists of our own country have adopted the same views: Philip on the ^'ital
Functions, ed. 3, p. 120; Mayo’s admirable Outlines of Human Physiology, ed. 3, p. 227-231, &c,

t Anatomie Pathologique, Fasc. III.

t Du Syst^me Nerveux, par P. Flourens, Paris 1824, p. 70.

OF THE MEDULLA OBLONGATA AND SPINALIS.

637

It was a singular mistake to imagine that the same conclusion could be just
in reference to the entire animal, which was incorrect in reference to the ani-
mal deprived of its encephalon. The facts are these: in the entire animal,
sensation and voluntary motion, functions of the cerebrum, combine with the
functions of the medulla oblongata and medulla spinalis, and may therefore
render it difficult or impossible to determine those which are peculiar to each ;
if, in an animal deprived of the brain, the spinal marrow, or the nerves supply-
ing the muscles, be stimulated, those muscles, whether voluntary or respiratory,
are equal!}' thrown into contraction, and, it maybe added, equally in the com-
plete and in the mutilated animal ; and, in the case of the nerves, equally in
limbs connected with and detached from the spinal marrow.

The operation of all these various causes of muscular contraction may be
designated centric, as taking place at, or at least in a direction from, central
parts of the nervous system. But there is another function the phenomena of
which are of a totally different order and obey totally different laws, being ex-
cited by causes in a situation which is eccentric in the nervous system, that is,
distant from the nervous centres. This mode of action has not, I think, been
hitherto distinctly understood by physiologists. It is involved in the question
which Baron Cuvier considers as so full of interest, and is that treated of in
the following pages.

Many of the phenomena of this principle of action, as they occur in the
limbs, have certainly been observed. But, in the first place, this function is
by no means confined to the limbs : for, whilst it imparts to each muscle its
appropriate tone, and to each system of muscles its appropriate equilibrium
or balance, it performs the still more important office of presiding over the ori-
fices and terminations of each of the internal canals in the animal economy,
giving to them their due form and action; and, in the second place, in the in-
stances in which the phenomena of this function have been noticed, they have
been confounded, as I have stated, with those of sensation and volition ; or, if
they have been distinguished from these, they have been too indefinitely deno-
minated instinctive, or automatic. I have been compelled, therefore, to adopt
some new designation for them, and I shall now give the reasons for my choice
of that which is given in the title of this paper.

This property is characterized by being excited in its action, and reflex in its

4 N 2

638

DR. MARSHALL HALL ON THE REFLEX FUNCTION

course ; in every instance in which it is exerted, an impression made upon the
extremities of certain nerves is conveyed to the medulla oblongata or the me-
dulla spinalis, and is reflected along other nerves to parts adjacent to, or re-
mote from, that which has received the impression.

It is by this reflex character that the function to which I have alluded is to
be distinguished from every other. There are, in the animal economy, four
modes of muscular action, of muscular contraction. The Jir'st is that desig-
nated voluntary, volition, originating in the cerebrum, and spontaneous in its
acts, extends its influence along the spinal marrow and the motor nerves, in a
direct line, to the voluntary muscles. The second is that of the respiration :
like volition, the motive influence in respiration passes in a direct line from
one point of the nervous system to certain muscles ; but as voluntary motion
seems to originate in the cerebrum, so the respiratory motions originate in the
medulla oblongata : like the voluntary motions, the motions of respiration are
spontaneous ; they continue, at least, after the eighth pair of nerves has been
divided. The third kind of muscular action in the animal economy is that
termed involuntary : it depends upon the principle of irritability, and requires
the immediate application of a stimulus to the nervo-muscular fibre itself.
These three kinds of muscular motion are well known to physiologists ; and I
believe they are all which have been hitherto pointed out. There is, however,
a fourth, which subsists, in part, after the voluntary and respiratory motions
have ceased, by the removal of the cerebrum and medulla oblongata, and
which is attached to the medulla spinalis, ceasing itself when this is removed,
and leaving the irritability undiminished. In this kind of muscular motion, the
motive influence does not originate in any central part of the nervous system,
but at a distance from that centre: it is neither spontaneous in its action, nor
direct in its course ; it is, on the contrary, excited by the application of appro-
priate stimuli, which are not, however, applied immediately to the muscular or
nervo-muscular fibre, but to certain membranous parts, whence the impression
is carried to the medulla, reflected, and reconducted to the part impressed, or
conducted to a part remote from it, in which muscular contraction is effected.

The first three modes of muscular action are known only by actual move-
ments or muscular contractions. But the reflex function exists as a continuous
muscular action, as a power presiding over organs not actually in a state of

OF THE MEDULLA OBLONGATA AND SPINALIS.

639

motion, preserving in some, as the glottis, an open *, in others, as the sphinc-
ters, a closed form, and in the limbs, a due degree of equilibrium, or balanced
muscular action, — a function, not, I think, hitherto recognised by physiologists.

The three kinds of muscular motion hitherto known may be distinguished
in another way. The muscles of voluntary motion and of respiration may be
excited by stimulating the nerves which supply them, in any part of their
course, whether at their source, as a part of the medulla oblongata or medulla
spinalis, or exterior to the spinal canal : the muscles of involuntary motion are
chiefly excited by the actual contact of stimuli. In the case of the reflex
function alone, the muscles are excited by a stimulus acting mediately and
indirectly in a curved and reflex course, along superficial sub-cutaneous or sub-
mucous nerves proceeding to the medulla, and muscular nerves proceeding
from the medulla. The first three of these causes of muscular motion may act
on detached limbs or muscles. The last requires the connexion with the me-
dulla to be preserved entire.

All the kinds of muscular motion may be unduly excited. But the reflex
function is peculiar in being excitable into modes of action not previously sub-
sisting in the animal economy, as in the cases of sneezing’, coughing, vomit-
ing, &c. The reflex function also admits of being permanently diminished or
augmented, and of taking on some other morbid forms, of which I shall treat
hereafter.

I shall thus have occasion to speak of the reflex function as the source of
equilibrium in the muscular system ; as excitable into various actions, which,
however familiar, are not constant ; and as assuming morbid forms.

Before I proceed to the detail of the experiments upon which this disquisi-
tion rests, it may be well to point out several instances in illustration of the
various sources and modes of muscular action which have been enumerated.
None can be more familiar than the act of swallowing. Yet how complicated
is this act ! The apprehension of the food by the teeth, the tongue, &c., is volun-
tary, and cannot, therefore, take place in an animal from which the cerebrum is
removed -j-. The transition of the food over the glottis and along the middle
and lower parts of the pharynx depends upon the reflex function : it can take

* See Legallois, Op. cit. p. 176 — 178.
t Du Syst^me Nerveux, par M. Flourens, Paris 1824, p. 90.

G40

DR. MARSHALL HALL ON THE REFLEX FUNCTION

place in animals from which the cerebrum has been removed or the ninth
pair of nerves divided -j- ; but it requires the connexion with the medulla
oblongata to be preserved entire :}: ; and the actual contact of some substance
which may act as a stimulus § : it is attended by the accurate closure of the
glottis, and by the contraction of the pharynx. The completion of the act
of deglutition is dependent upon the stimulus immediately impressed upon the
muscular fibres of the oesophagus, and is the result of excited irritability.

The example which I have given is one of excited reflex function. The
condition of the glottis during respiration, and that of the pharynx and of the
sphincters at all times, except during the acts of deglutition, or of excretion,
aflbrd equally interesting and familiar examples of the permanent influence of
that function. Whilst the nervous connexion between the larynx and the me-
dulla oblongata is preserved entire, — in the rabbit {Lepus cimiculus) , for exam-
ple,— the glottis is preserved open, being slightly dilated during each act of
inspiration ; but if the superior laryngeal nerves be divided, the aperture
immediately becomes so much diminished, that a state of excessive dyspnoea
is induced. The sphincter ani, on the other hand, remains closed in the decapi-
tated turtle {Chelonia mydas), if the lower part of the medulla spinalis be left
in its canal ; but it becomes immediately relaxed and open, if this part of the
nervous system be withdrawn. The action of this muscle depends upon the
medulla spinalis, and not upon the brain only.

However plain tliese observations may have made the fact, that there is a func-
tion of the nervous and muscular system distinct from sensation, from the vo-
luntary and respiratory motions, and from irritability, it is right, in every such
inquiry as the present, that the statements and reasonings should be made with
the experiment, as it were, actually before us. It has already been remarked, that
the voluntary and respiratory motions are spontaneous acts, not necessarily re-

* Du Syst^me Nerveux, par M. Flourens, Paris 1824, p. 90.

t The Ner\'ous System, by Charles Bell, F.R.S. 4to ed. 1830. Appendix, p. cxviii.

t De rUsage de I’Epiglotte, par M. Magendie, Paris 1813, pp. 6, 23, &c.

§ This is the reason of our inability to perform the act of swallowing two or three times in rapid suc-
cession, without taking something into the mouth, or allowing time for the secretion of a portion of
saliva. Tlie reflex function must be excited into action by the contact of a stimulus. ITie act of
swallowing cannot, therefore, be renew'ed unless some substance, as saliva, be carried into contact w'ith
the pharynx. See further, p. G61.

OF THE MEDULLA OBLONGATA AND SPINALIS.

641

quiring the agency of a stimulus. If, then, an aninial can be placed in such
circumstances that such motions will certainly not take place, the power of
moving remaining, it may be concluded that volition and the motive influence
of respiration are annihilated. Now this is effected by removing the cerebrum
and the medulla oblongata. These facts are fully proved by the experiments of
Legallois and M. Flourens, and by several which I proceed to detail, for the
sake of the opportunity afforded by doing so, of stating the argument most clearly.

I divided the spinal marrow of a very lively snake {Coluber between

the second and third vertebrae. The movements of the animal were, immedi-
ately before, extremely vigorous and unintermitted. From the moment of the
division of the spinal marrow, it lay perfectly tranquil and motionless, with
the exception of occasional gaspings and slight movements of the head.

It became quite obvious that this state of quiescence would continue indefi-
nitely, were the animal secured from all external impressions.

Being now stimulated, the body began to move with great activity, and con-
tinued to do so for a considerable time, each change of position or situation
bringing some fresh part of the surface of the animal into contact with the
table or other objects, and renewing the application of stimulus.

At length the animal became again quiescent ; and being carefully protected
from all external impressions, it moved no more, but died in the precise posi-
tion and form which it had last assumed.

It requires a little manoeuvre to perform this experiment successfully : the
motions of the animal must be watched, and slowly and cautiously arrested by
opposing some soft substance, as a glove or cotton wool ; they are by this means
gradually lulled into quiescence. If at this moment the figure last assumed
be sketched upon paper, and the animal be left, protected from external impres-
sions, it will be found to retain the same identical form when all vitality has
ceased.

The slightest touch with a hard substance, the slightest stimulus, will, on the
other hand, renew the movements of the animal in an active form. But that
this phenomenon does not depend upon sensation, is further fully proved by
the facts, that the position last assumed, and the stimuli applied, may be such
as would be attended by extreme or continued pain, if the sensibility were un-
destroyed: in one case the animal remained partially suspended over the acute

642

DR. MARSHALL HALL ON THE REFLEX FUNCTION

edge of the table ; in others the infliction of punctures, and the application of
a lighted taper, did not prevent the animal, still possessed of active powers of
motion, from passing into a state of complete and permanent quiescence.

The same observations were made upon various other animals — the turtle,
the viper {f Ipera Berus) , the toad {Bufo vulgaris), the frog {Rana temporaria) ,
the eft (Triton cristatus), &c. It may therefore be stated as a general fact,
that if an animal be deprived of the cerebrum and medulla oblongata, and
placed under an inverted bell-glass, or otherwise protected from external sti-
muli, it will not move, however easily it may be excited to motion by external
impressions.

I must now solicit the attention of the Society to three important points :
it is obvious,

1st, That sensation can act, in inducing muscular motion, only through the
medium of volition ;

2ndly, That, in the experiments which have been described, volition, — the
ivill, and not the power, to move, was annihilated;

3rdly, That, in such cases, — volition being destroyed and the agency of sen-
sation excluded, — the influence of external impressions, which might be sup-
posed to induce pain, must have been exerted upon some property of the ner-
vous system different from sensibility.

The absence of spontaneous motions in decapitated animals, proves the
privation of volition ; and the privation of volition removes all evidence of
sensibility in excited motions, and indeed positively excludes its influence.
Sensation, volition, and motion, may be viewed as three links of the chain,
in the case in which motion is induced by pain. If the second link be de-
stroyed, the connexion between the first and third is dissolved. The proof, in
fine, that the excited motions which belong to the reflex function are indepen-
dent of sensation, is precisely of the same character as that by which the
motions due to irritability are distinguished from the same principle.

We are hence led to the conclusion that the excited motions of decapitated
animals are dependent upon a principle different from sensation and volition ;
and we are further led to the inquiry — What is the nature of that principle —
what the cause of those motions, which remain after sensation and volition are
destroyed ?

OF THE MEDULLA OBLONGATA AND SPINALIS.

643

But before I enter upon this question, it is important to show still more
distinctly than I have done, the distinction between the movements arising
from the reflex function of the medulla oblongata and medulla spinalis, and
those arising from irritability itself. If the glottis of an animal he touched, there
is an immediate contraction. If the heart be touched, the same phenomenon is
observed. What is the difference between the excited movements of these two
organs ? If the brain be removed, the same events still take place. If the me-
dulla oblongata be removed, the contractions of the stimulated larynx sud-
denly cease, whilst those of the heart continue as before. The difference con-
sists, then, in the presence of the medulla oblongata, which is essential to the
contractions of the larynx, but of which those of the heart are entirely inde-
pendent. The influence of the stimulus upon the heart is immediate. That
of a stimulus applied to the larynx must pass to the medulla oblongata, and
be reflected upon the part moved.

It is interesting to compare the excited movements of the glottis and the
submaxillary textures, of the sphincter ani and the tail, and of the heart, in these
several parts of the recently killed turtle, placed together upon the same table.
All continue vigorous for a considerable time, until the medulla oblongata or
the medulla spinalis be withdrawn, when the movements of that portion of the
respiratory apparatus which is attached to the head, or of the sphincter and
tail, cease in an instant.

The reflex function of the medulla is most permanent and apparent to obser-
vation in those animals in which the respiration is lowest. The cold-blooded
animals, the hybernating animal, and the very young of the warm-blooded, are
therefore the subjects in which this function can be best studied. It may be
retained, or restored, however, in the adult warm-blooded animal, by retaining
the respiration, or by renewing the respiration artificially, — a fact, which con-
stitutes another characteristic of the reflex function, and distinguishes it from
irritability, and which is, in my opinion, one of the most Temarkable in phy-
siology, and highly worthy of further investigation. These remarks will readily
suggest the proper choice of animals, and mode of experiment, for the display
of the reflex function. I now proceed to the detail of the various experiments
which I have made upon this subject, and shall then deduce the conclusions
which appear to flow from them.

4 o

MDCCCXXXIII.

644

DR. MARSHALL HALL ON THE REFLEX FUNCTION

II. Experbnents.

The phenomena of the reflex function, like those of the irritability, are, as
I have just stated, more observable in tlie lower orders of animals, in the very
young of the higher orders, and in the state of hybernation. It will be found,
however, that the full-grown mammalia are not less distinctly endued with this
property of the nervous system, whilst the functions of respiration and circula-
tion are continued.

The first experiment which I made was upon the turtle.

This animal was decapitated in the manner usual with cooks, by means of a
knife, which divided the second or third vertebra.

The head being placed upon the table for observation, it was first remarked
that the mouth opened and shut, and that the submaxillary integuments de-
scended and ascended, alternately, from time to time, replacing the acts of
respiration. I now touched the eye or eyelid with a probe. It was imme-
diately closed ; the other eye closed simultaneously. I then touched the nostril
with the probe. The mouth was immediately opened widely, and the submax-
illary membranes descended. This effect was especially induced on touching
the nasal fringes situated just within the anterior part of the maxilla. I passed
the probe up the trachea and touched the larynx. This was immediately fol-
lowed by a forcible convulsive contraction of the muscles annexed to it.
Having made and repeated these observations, I gently withdrew the medulla
and brain. All the phenomena ceased from that moment. The eye, the nos-
tril, the larynx were stimulated, but no movement followed.

The next observations were made upon the other parts of the animal. The
limbs, the 'tail, were stimulated by a pointed instrument or a lighted taper.
I’hey were immediately moved with rapidity. The sphincter was perfectly
circular and closed ; it was contracted still more foi’cibly on the application of
a stimulus. The limbs and the tail possessed a certain degree of firmness or
tone, recoiled on being drawn from their position, and moved with energy on
the application of the stimulus. On withdrawing the spinal marrow gently out
of its canal, all these phenomena ceased. The limbs were no longer obedient
to stimuli, and became perfectly flaccid, having lost all their resilience. The
sphincter lost its circular form and its contracted state, becoming lax, flaccid,
and shapeless. The tail was flaccid, and unmoved on the application of stimuli.

OF THE MEDULLA OBLONGATA AND SPINALIS.

645

This experiment affords evidence of many important facts in physiology. It
proves that the presence of the medulla oblongata and spinalis is necessary to
the contractile function of the eyelids, the sub-maxillary textures, the larynx,
the sphincters, the limbs, the tail, on the application of stimuli to the cutaneous
surfaces or mucous membranes. It proves the reflex character of this property
of the medulla oblongata and spinalis, and the dependence of these motions
upon the reflex function. It proves that the tone of the limbs, and the con-
tractile property of the sphincter, depend upon the same reflex function of the
medulla spinalis, — effects not hitherto suspected by physiologists.

I must now state that the phenomena which have been detailed subsist in
distinct portions of the divided nervous system. If, after severing the head of
the turtle, the lower extremities and the tail be separated together, in the man-
ner usual with cooks, the phenomena which I have described are still observed
in the distinct and separate portions of the animal. The head, the anterior
extremities, and the tail present the movements which have been described,
when severally stimulated. The posterior extremities alone were observed to be
flaccid and unimpressible by stimuli ; and these were found, on examination,
to have been separated from their connexion with the spinal marrow.

An interesting experiment demonstrates the powerful influence of the reflex
function over the sphincter ani in the turtle. If, after the removal of the tail
and the posterior extremities, with the rectum, and of course with a portion of
the spinal marrow, water be forced into the intestine, by means of Read’s
syringe, both the cloaca and the bladder are fully distended before any part of
the fluid escapes through the sphincter, which it then does on the use of much
force only, and by jerks. The event is very different on withdrawing the spinal
marrow: the sphincter being now relaxed, the water flows through it at once in
an easy continuous stream, with the application of little force, and without
inducing any distension, even of the cloaca.

I was first struck with the phenomena of the reflex function of the spinal
marrow in the separated tail of an eft. On being excited by the point of a
needle passed lightly over its surface, it contracted and moved as if it still
formed a part of an entire animal.

On another occasion, having removed the head of a frog, I divided the spine
between the third and fourth vertebrae, and separated the upper portion of the

4 o 2

646

DR. MARSHALL HALL ON THE REFLEX FUNCTION

animal from the lower. There were then the head, the anterior extremities,
and the posterior extremities, with their corresponding portions of medulla, as
three distinct parts of an animal. Each preserved the reflex function. On
touching an eye, it was retracted, and the eyelids closed, whilst similar phe-
nomena were observed simultaneously in the other eye. On removing the
medulla, these phenomena ceased. On pinching the toe of one of the anterior
extremities, the limb and the opposite limb equally moved. On removing the
spinal marrow, this phenomenon also ceased. Precisely similar effects were
observed in regard to the posterior extremities.

Similar phenomena are also observed in the snake. If the head be removed,
and a pointed instrument or a lighted taper be brought into contact with any
part of the surface, it is instantly moved. The motion consists in a flexion of
the entire part, and in a concentric movement of the integuments towards the
point irritated; so that the muscles situated along the spine, and certain
muscles analogous to the panniculus carnosus, are excited to contraction.
The extremity of the tail is most impressible. The function which presides
over these movements subsisted in every part of the animal separated from the
rest, but instantly ceased on removing the spinal marrow.

On touching a point immediately within the teeth of the upper jaw, the
larynx was suddenly drawn downwards and closed. These movements could
also be excited by touching the nostrils. They ceased on removing the me-
dulla oblongata.

Similar phenomena are seen also in the very young of the mammalia. A
rabbit, one day old, was immediately deprived of all voluntary or respiratory
motion, with the exception of gaspings, by dividing the spinal marrow near
the occiput. Yet the head and the limbs moved, on stimulating the ears or
the feet. These movements ceased in a quarter of an hour, but were renewed
by artificial respiration. The phenomena were precisely similar after decapi-
tation, haemorrhage being prevented and artificial respiration maintained. All
ceased on removing the medulla oblongata and spinalis.

One of the most remarkable of the phenomena attached to the reflex func-
tion in animals, is that presented by those muscles of the hedgehog {Erinaceus
europccjts) by means of which that animal assumes, in certain circumstances,
the form and firmness of a ball. The reflex function seems especially to con-

OF THE MEDULLA OBLONGATA AND SPINALIS.

647

nect the roots of the spines with the muscles. If the animal be examined un-
der the influence of hybernation, the reflex function continues for some hours
after the brain is removed ; the panniculus carnosus, the limbs, tiie tail, the
larynx, the sphincter ani, remain excitable, and retain a degree of tone. These
phenomena cease on removing the medulla spinalis.

The phenomena of the reflex function seen in the panniculus carnosus, and
in other muscles of the hedgehog, are also particularly displayed in the very
young animal, in which the peculiar movements of this creature are excitable
for a considerable time after decapitation, or the division of the spinal marrow,
and long after the cessation of the voluntary and respiratory motions, wlien it
is in a languid and dying state.

In the case of the decapitated young hedgehog, after all gasping has ceased,
motions of the larynx are still excited on irritating the nostrils, or on irritating
the medulla itself; just as the peculiar motions of the trunk are excited on
irritating the limbs, tail, or spines, — or the spinal marrow.

Nor are we without evidence that the same principles obtain in the human
subject. The condition of the infant born without cerebrum or cerebellum,
and breathing from the influence of the medulla oblongata alone, is precisely
that of the reflex function, with the addition of respiration. Such a case has
been witnessed and described by Mr. Lawrence *. “The child moved briskly
at first, but remained quiet afterwards, except when the tumour was pressed,
which occasioned general convulsions. It breathed naturally, and was not
observed to be deficient in warmth, until its powers declined. I regret that,
from a fear of alarming the mother, no attempt was made to see whether it
would take the breast: a little food was given it by the hand. It voided urine
twice in the first day, and once a day afterwards : it had three dark-coloured
evacuations. Tlie medulla spinalis was continued for about an inch above the
foramen magnum, swelling out into a small bulb, which formed the soft tumour
on the basis of the skull. All the nerves, from the fifth to the ninth, were con-
nected to this.” This brief detail is full of interest. The respiration was natu-
ral, the medulla oblongata being entire. Swallowing was effected when food
was brought into contact with the pharynx ; the sphincters performed their
functions ; the limbs were moved when the skin was first impressed by the

* Medico-Chirurgical Transactions, vol. v. page 166.

G48

DR. MARSHALL HALL ON THE REFLEX FUNCTION

atmospheric air. There was no indication of sensation — the child remained
quiet after the first brisk movements ; and no event is mentioned which could
establish the existence of voluntary motion, — the acts of swallowing, and of the
expulsion of the urine and faeces, with the functions of the larynx and of the
sphincters, belonging distinctly to the reflex function.

M. Lallemand has briefly described a case of anencephalous foetus*. J’ai
vu, il y a quatre ans, a 1’ Hdtel-Dieu, un foetus anencephale, a terme, ou a
peupr^s, qui vecut trois jours. Pendant tout ce temps il poussa des cris assez
forts, exerga des mouvemens de succion toutes les fois qu’il sentit quelque
chose entre ses l^vres; mais on fiit oblig4 de le nourrir avec du lait et de I’eau
sucree, parce qu’aucune nourrice ne voulait lui donner le sein. Il executait
des mouvemens assez etendus des membres thoraciques et abdominaux.
Quand on pla^ait un corps Stranger dans ses mains, il flechissait les doigts
comme pour le saisir ; mais en general tons ses mouvemens avaient moins
d’energie que ceux d’un foetus de meme age.

“ Le cerveau et le cervelet manquaient enti^rement: il ne restait a la base du
crane que la moelle allongee et la protuberance annulaire, avec I’origine des
nerfs pneumo-gastrique, trifacial et optique. Le tout etait reconvert par les
debris des os du crane, des meninges et de la peau.”

A similar case is detailed by M. Ollivier'I', who remarks — J’observai I’en-
fant anencephale deux heures apr^s sa naissance. Les yeux etaient constam-
ment fermes; il poussait des cris fi-equens qu’on calmait facilement en intro-
duisant le petit doigt dans sa bouche: il exer^ait alors des mouvemens de suc-
cion i-epetes ; U agitait ses membres avec assez de force, et serrait entre ses
doigts les corps qu’on pla9ait dans ses mains.

“ Je le revis au bout de trois heures. Les pieds et les mains Etaient devenus
violets et froids; la respiration ne s’operait plus a des intervalles aussi rappro-
cli6s ; les mouvemens de la moelle ^pini^re, que j’avais remarques d’abord, con-
tinuaient toujours d’avoir lieu, et suivaient chacune des grandes et longues in-
spirations qu’il faisait. Les cris etaient moins forts et moins fr^quens: on lui
donna k diverses reprises de petites cuillerees de vin vieux sucr6.

“ Insensiblement le refroidissement des extr^mites gagna le reste des mem-

* Observations Pathologiques, p. 86.
t Traits de la Moelle Epini^re, ed, 2, Paris 1827, p. 155.

OF THE MEDULLA OBLONGATA AND SPINALIS.

649

bres et le tronc; la respiration s’operait a de plus longs intervalles : elle devint
convulsive. Get etat persista pendant six ou huit heures; ses cris devinrent
plus faibles et plus eloign^s, de meme que les mouvemens de la respiration,
qui etaient accompagnee de convulsions generales, et il mourut dans un verit-
able etat d’asphyxie, apr^s avoir pousse un cri analogue a celui qui resulte du
hoquet.”

M. Ollivier adds, (p. 161) — “ II n’existait pas ici un seul rudiment de I’ence-
phale et des prolongemens de la moelle alongee; la moelle epiniere seule etait
restee intacte, et cependant cet infant exerqait des succions repetees, et serrait
avec assez de force entre ses doigts les corps qu’on plagait dans sa main ; ces
mouvemens etaient loin d’etre automatiques 'comme ceux qui agitaient les
membres inferieurs.”

These cases, in connexion with the preceding one, are full of interest. The
peculiar cries, which resemble, in their rationale, the croup-like convulsion
from dentition ; the closed state of the eyelids ; the action of suction excited by
the contact of the finger; the closure of the fingers excited by objects placed
in the palm of the hand, and the movements of the inferior extremities, in this
acephalous infant, are phenomena of the reflex function of the most deeply
interesting character.

The following facts are extracted from a letter addressed by Mr. Sweatman
to Sir Charles Bell, and published in the “ Nervous System”*: — “After the
membranes had given way, and the liquor amnii had escaped, the midwife on
examining found another membranous bag presenting, which she naturally
supposed belonged to a second child, and therefore did not interfere. During
the passage of this bag under the os-pubis, it suddenly burst, and the whole of
the brain escaped from the opening very much smashed, and hanging together
only by its membranes. The child breathed with perfect freedom and cried
strongly, rolling its eyes about in a wild, staring manner. It moved its lower
extremities freely, and that not from spasm, but obviously in obedience to ex
ternal impressions. There was no motion whatever of the upper extremities.

“ In this state it remained for about three hours, when all motion in the
extremities ceased, the eyes became fixed, and the breathing gradually slower,
till it ceased altogether, just seven hours after the birth of the child. During

* Appendix, p. cxxxvi.

650

DR. MARSHALL HALL ON THE REFLEX FUNCTION

this time neither urine nor meconium passed, nor had there been any hte-
morrhage from tlie vessels of the brain.

“ On examination the occipital bone and the posterior part of several of
the cervical vertebrae were found wanting, and their place had been occupied
by fluid, surrounded by a membranous bag; an instance of spina bifida of the
neck. The spinal marrow was perfect.

“ A somewhat similar case occurred to me about three years ago, when I
had occasion from peculiar circumstances to remove the brain of a child through
the anterior fontanelle. In that instance, about ten minutes elapsed before its
birth, yet it drew a deep inspiration, and would have cried had it not been
prevented; and the motions of the lower extremities continued about half an
hour, although the whole of the brain had been removed, and a blunt instru-
ment repeatedly thrust down the foramen magnum

It is distinctly proved, by this series of observations, that the reflex function
exists in the medulla independently of the brain; in the medulla oblongata in-
dependently of the medulla spinalis; and in the spinal marrow of the anterior
extremities, of the posterior extremities, and of the tail, independently of that
of each other of these parts, respectively.

There is a still more interesting and satisfactory mode of performing the ex-
periment : it is to divide the spinal marrow between the nerves of the superior
and inferior extremities. We have then two modes of animal life : the first
being the assemblage of the voluntary and respiratory powers with those of
the reflex function and irritability ; the second, the two latter powers only :
the first are those which obtain in the perfect animal, the second those which
animate the foetus. The phenomena are precisely what might have been anti-
cipated. If the spinal marrow be now destroyed, the irritability alone remains,
— all the other phenomena having ceased.

The spinal marrow of a frog was divided between the antei ior and posterior
extremities. It was immediately observed tliat the head and the anterior ex-
tremities alone were moved spontaneously and with design, the respiration
being performed as before. But the posterior extremities were not paralyzed :
they were drawn upwards, and remained perfectly motionless, indeed, un-
less stimulated ; by tlie application by any stimulus, they, were moved with
* See a similar case by Mr. Hammond, in the Medico-Chirurgical Transactions, vol. xii. p. 308.

OF THE MEDULLA OBLONGATA AND SPINALIS.

651

energy, but once only, and in a manner perfectly peculiar. The stimulus was
not felt by the animal, because the head and anterior extremities remained
motionless at the time it was applied. Nothing could be more obvious, and
indeed striking, than the difference between the phenomena of the functions of
sensation and volition observed in the anterior part of the animal, and those of
the reflex function in the posterior ; in the former there were spontaneous
movements with obvious design ; in the latter, the mere effect of stimulus.

The same experiment was made upon the toad ; but for some reason, probably
anatomical, it does not succeed so uniformly in this animal as in the frog.

The experiment was repeated upon a guinea-pig. The effect was an imme-
diate and total paralysis of sensation and voluntary motion in the posterior
extremities : there was no expression of pain when they were pinched, nor was
there the slightest indication of a power of spontaneous motion : they were
dragged along when the animal moved. But they were not unimpressible by
stimuli, nor destitute of the power of moving when stimulated : on the con-
trary, when pinched, they displayed a sort of repeated, hurried motion, alto-
gether peculiar. The power of the sphincters was evidently preserved. In a
word, the reflex function remained entire.

In all these experiments the upper part of the animal presented the pheno-
mena of sensation and of spontaneous movements ; in the lower, there was
total paralysis of these powers ; yet the reflex function, the excitability, the
firmness of the limbs, and the irritability remained. It now remains to be
stated, that the reflex function admits of exaltation and of diminution.

If a frog be made to swallow a watery solution of strychnine or of opium,
or if such a solution of strychnine or opium be applied to the skin, the animal
soon becomes affected with symptoms perfectly similar to those of tetanus.
The surface becomes highly susceptible to the impression of stimuli, and the
muscles of the limbs become affected with continued spasmodic action. The
affection is obviously one of augmented reflex function of the medulla. It ac-
cordingly ceases instantly on destroying the nervous masses.

A frog made tetanic by opium was decapitated, and divided just below the
third vertebra. The eyes were retracted, and no movement could be detected
on irritating the eyelids or skin. Both the anterior and posterior extremities
remained susceptible, and tetanic, as before ; the limbs were moved in the same

4 p

MDCCCXXXIII.

652

DR. MARSHALL HALL ON THE REFLEX FUNCTION

spasmodic manner by the same slight impressions. All was changed on re-
moving the brain and spinal marrow. The eyes were no longer retracted. The
muscles of the limbs were immoveable under the action of stimuli, and per-
fectly flaccid, having lost their exalted tone.

Precisely similar phenomena were observed when the frog was made tetanic
by opium or strychnine and divided into three portions, the head, the anterior
and the posterior extremities ; and in the eft made tetanic and divided into the
head, anterior and posterior extremities, and tail. Each part remained tetanic,
impressible by the sliglitest touch, and spasmodically contracted on any appli-
cation of stimulus. The tetanus in each is instantaneously terminated by de-
stroying the corresponding portion of spinal marrow, the head, the limb, or
the tail, instantly manifesting a perfectly relaxed and flaccid condition of the
muscles. The irritability remains unimpaired.

These facts complete the proof that the phenomena which I have referred to
the reflex function, do not depend either upon sensation and volition, or upon
irritability. It is plain that the spasmodic actions in tetanus are not voluntary
actions, and they obey the same laws as the movements observed in an animal,
or parts of an animal, not tetanic, under the influence of stimuli. It is equally
plain that phenomena which depended upon excited irritability would not cease
whilst that irritability remained unimpaired

The phenomena of tetanus, in its effects upon the limbs, enable us to conceive
more distinctly than we should otherwise do, the effect of the reflex function
in its natural state, in maintaining the due degree of balance and antagonism
of the muscles and firmness of the limbs.

If a few drops of dilute hydrocyanic acid be placed upon the tongue of a
frog, a state of things the reverse of that just described as the effect of opium
or strychnine is induced : the contractions which depend on the reflex function
are observed to become less and less energetic and excitable, and at length
cease altogether.

* Having observed these facts in connexion with the reflex function, it became a question whether
the rigidity of the muscles immediately consequent to death depends upon the same principle. Two
rabbits were killed ; in one the spinal marrow was destroyed, in the other it was left entire. Both,
however, became equally rigid. So that the spasm of death is a mere effect of irritability, and not of
the reflex fimction of the spinal narrow.

OF THE MEDULLA OBLONGATA AND SPINALIS.

653

Having thus detailed the phenomena of the reflex function, as they are ob-
served in their ordinary and augmented and diminished degrees of force, I
shall briefly enumerate some of those excited motions observed in various parts
of the animal frame, which are obviously referrible to the same function.

The most healthy condition of the reflex function is that, the result of
which is the due state of balance between antagonist muscles. But certain
excited states of this function can scarcely be viewed as otherwise than
healthy : such are — winking when an object touches the eyelid, the singular
effect of dashing cold water on the face, and the singular effect of tickling *
upon the respiration, sneezing from irritation of the nostrils, cough from that
of the larynx, vomiting from that of' the pharynx, strangury from irritation of
the rectum, and tenesmus from that of the bladder, &c.

The excited reflex function is observed on touching the eye, the nasal fringes,
or the larynx, in the separated head of the turtle ; and on touching the sphincter,
the tail, or the limbs, of the separated lower portion of that animal ; in the
frog, the lower extremities are sometimes moved with violence even, on the
application of a stimulus, after the division of the spinal marrow. All the
systems of muscles, therefore, obviously partake of this remarkable action.

It is plain, from the preceding observations, that the reflex function may be
viewed as subsisting in its natural state, in its state of general excess or failure,
and in its state of momentary and partial excitement.

III. Pathology.

There still remains an interesting part of this inquiry. What relation does
the reflex function bear to the art of physic ? It will soon be seen that it throws
a ray of light over some obscure points in medicine. Indeed the study of the
reflex function appears to me to reveal and explain a totally new order of facts
in pathology, and to lead to a new division of the diseases of the nervous sy-
stem, coinciding with the different modes of operation of their causes, into those
of centric and those of eccentric origin.

One of the most interesting of medical subjects, in relation to the reflex

* I can readily imagine that tickling may have been carried to such an extent as to interrupt the
respiration and prove fatal by asphyxia, as in a recent instance said to have occurred on the Continent.

4 p 2

654

DR. MARSHALL HALL ON THE REFLEX FUNCTION

function, is that of dentition. Dentition is a sort of natural experiment upon
this function. The general convulsion, the strabismus, the spasm of the fingers
and toes, the croup-like affection of the respiration, the repeated vomitings,
the tenesmus, the strangury, the involuntary discharge of urine and of the
fmces, from its operation, denote the influence of irritation of the maxillary
nerves, through the medium of the medulla, upon the muscles of voluntary and
respiratory motion, of the eye, the larynx, the sphincters, &c., in the human sub-
ject, and indicate so many arcs of the reflex function. However these facts
may have been known, their true rationale has not been discovered. In all such
cases the remedy is, to relieve the part in which the cause is operating. In the
present instance the maxillary nerves and vessels are to be relieved by free sca-
rification; the lancet should be used freely, daily, or still more frequently.

The young of other animals, and especially of the feline and canine species,
are exceedingly subject to similar effects from dentition, which are not unfre-
quently fatal. The fatal event is frequently owing to interrupted respiration.
In one instance, the asphyxia was averted, in a very young puppy, by artificial
respiration, effected by alternate compression and relaxation of the parietes of
the thorax.

The reflex function is far more excitable in the very young animal. The
second dentition rarely, therefore, induces such affections as the first.

With the effects of dentition in infants, some affections of the adult may be
compared, as chorea, some forms of epilepsy, and some forms of asthma. The
diseases to which these designations have been given vary exceedingly in dif-
ferent instances ; inasmuch as some cases are of centric and others of eccentric
origin. One characteristic distinguishes the latter form of the disease, — it
usually combines more affections of the reflex function than one. Such a form
of epilepsy, for example, combines hickup, or even vomiting, with the epileptic
attack. The usual source of those forms of disease is in the intestinal canal,
the stomach being irritated by improper diet or the bowels by morbid contents.
This division of the subject leads to an important distinction of these cases
into those which admit comparatively more easily, and more difficultly, of cure.

Epilepsy is plainly of two kinds : the first has a centric origin in the me-
dulla itself ; the second is an affection of the reflex function, the exciting cause
being eccentric, and acting chiefly upon the nerves of the stomach or intes-

OF THE MEDULLA OBLONGATA AND SPINALIS.

655

tines, which consequently form the first part of the reflex arc. The fact of the
frequent occurrence of a fit of epilepsy in coitu is very interesting in reference
to the reflex function : it distinctly connects these two events ; and it aflbrds
another instance of an influence exerted, through the medium of this function,
between distant parts of the spinal marrow. There is but a step, as it were,
from the normal affection of the nervous, muscular, and respiratory systems, in
that circumstance, to an attack of epilepsy itself.

The disease termed asthma claims rather more than an incidental notice in
this place. True asthma, viz. that form of this disease which occurs in youth,
and assumes a distinctly spasmodic form and course, like so many other mor-
bid conditions of the reflex function, frequently arises from gastric or intes-
tinal irritation. It is also frequently excited by the contact of certain powders,
as that of ipecacuanha, with the larynx, just as sneezing is induced by similar
impressions upon the nostrils. It appears to consist in an action excited,
through the reflex function, in the larger bronchia. The influence of the smoke
of the stramonium in relieving the attack of asthma is another argument in
favour of its being an affection of the reflex function. ' Indeed, a comparison
of the various causes, the mode of attack, the course, and the effects of reme-
dies, in this singular morbid affection, alike denote its relation to this peculiar
function.

With the effects of dentition, those of gastric or enteric irritation, in their
multiplied forms, may be compared.

Tenesmus and strangury are affections of other arcs of the reflex function.

One circumstance in the pathology of the reflex function is very remarkable.
Several forms of the morbid affections of this function occur during the first
sleep. This is the case with the croup-like affection arising from dentition,
with spasmodic asthma, and with a peculiar painful affection of the rectum,
not hitherto described.

Tetanus and hydrophobia appear equally to result from injuries inflicted
upon the extremities of certain nerves, by means of which the morbid influence
is conveyed to the medulla, whence it is reflected through the motor nerves to
the muscular system. As free lancing of the gums in dentition, so the early
division of the wounded nerve or amputation in tetanus, has, at once, checked
the morbid affection. Is it possible that hydrophobia might be arrested by a

656

DR. MARSHALL HALL ON THE REFLEX FUNCTION

similar procedure ? The subject is of intense interest, and deserving of the
fullest attention.

Certain poisons, as the strychnine, induce excess in the reflex function;
other poisons, as the hydrocyanic acid, destroy it altogether. In both cases
the muscular irritability remains perfect and undiminished. It is probably
through the medium of the same functions that many other poisons act upon
the animal economy.

In a frog, recently killed by strychnine, the irritability of the muscular fibre
remained unimpaired, — a proof that the tetanus of strychnine is an exalted
condition of the reflex function, and that the consequence is the exhaustion
of that function, and not of the irritability. Another frog, destroyed by the
hydrocyanic acid, presented similar phenoihena of unimpaired irritability on
the application of galvanism. In either case, if the animal be placed in water
through which a slight galvanic spark is passed, the limbs are immediately
and foreibly extended.

The study of the reflex function will doubtless throw an important light
upon toxicology, as well as some parts of pathology, and of the causes and
treatment of diseases, — subjects which, as they are more immediately connected
with medicine, I purpose forthwith to pursue elsewhere.

Diseases of the nervous system, then, may be divided into those wdiich have
their origin at the nervous centres, and those which originate at a distance
from those centres ; and especially in some part of the nervous arc, the func-
tion of which has formed the subject of this paper, — into those of centric and
into those of eccentric origin. It is highly probable that the diseases of the
latter class are more numerous than they may at first be supposed to be.
Chorea, hysteria, tremor, and convulsion have, doubtless, sometimes a centric,
sometimes an eccentric origin. In the latter case, the nervous centres may be-
come morbidly affected in the course of the disease, and the appearances after
death may mislead the medical inquirer as to the original cause and seat of the
disease. But the whole of this investigation must be reserved for the Trans-
actions of another Society. I shall add but one fact more of a medical cha-
racter in this place.

Legallois appears to have experienced great difficulty in explaining the
occurrence of paralysis from disease of the cerebrum, impressed, as he was

OF THE MEDULLA OBLONGATA AND SPINALIS.

657

that the spinal marrow constituted the source of voluntary motion. He ob-
serves, “ Quand bien meme on n’apercevrait aucun moyen de les concilier, il
n’en demeurerait pas moins vrai, d’une part, qu’une affection born6e unique-
ment au cerveau pent oter le sentiment et le mouvement volontaire a la moitie
du corps, et de I’autre, que le sentiment et le mouvement volontaire peuvent
subsister et etre entretenus dans un animal decapite. Quelque opposes que
ces faits paraissent etre, il faut se souvenir que deux faits bien constates ne
peuvent jamais s’exclure fun I’autre, et que la contradiction qu’on croit y re-
marquer tient ^ ce qu’il y a entre eux quelque intermediaire, quelque point de
contact qui nous 6chappe The facts which have been detailed in this paper
enable us readily to remove this difficulty, and to account for the paralysis in-
duced by disease of the cerebrum, on one hand, and for the movements of an
anencephalous foetus in utero, or of a decapitated animal, on the other. The
paralysis consists in the loss of voluntary motion ; the movements of the anen-
cephalous foetus result from the agency of the reflex function of the medulla
spinalis. Legallois’ error was that of mistaking the phenomena of the reflex
function for sensation and voluntary motion ; and his difficulty naturally arose
out of this error. There is no real discrepancy between the two orders of facts
to which Legallois refers.

The same facts enable us to understand how a perfect action of the sphincters
is compatible with paralysis of the limbs from disease of the cerebrum, and even
of the higher parts of the medulla spinalis ; whilst paralysis of the sphincters is
usually conjoined with paralysis of the limbs, arising from disease of the lower
part of the spinal marrow. The first intercepts the principle of voluntary mo-
tion; the second affects the very seat of the reflex function which presides over
the action of the sphincters.

IV. Inferences.

I shall now briefly enumerate the inferences which flow from the preceding
facts and experiments.

Physiologists have hitherto enumerated only three sources or principles of
muscular action, — volition, the motive influence of respiration, and irritability.

There is, however, a fourth source of muscular motion distinct from any of
■ * Op. cit. p. 21.

058

DR. MARSHALL HALL ON THE REFLEX FUNCTION

these, though not hitherto distinguished, to which I have ventured to give the
designation of the reflex.

Volition and the motive influence of respiration are direct in their course,
and spontaneous in their action ; the former proceeding from the cerebrum,
the latter from the medulla oblongata*.

The movements of irritability are the result of the immediate application of
a stimulus to the nervo-muscular fibre itself.

The reflex function is different from any of these :

It remains attached to the medulla spinalis, when the cerebrum and the me-
dulla oblongata are removed; it is not direct like volition, or the motive power
of respiration.

Its seat is the medulla generally; it ceases when the medulla is removed,
leaving the irritability entire; it is not excited immediately, like the movements
of irritability, but mediately, in a reflex course, through the medulla, from the
])art stimulated to the part moved.

In a state of health, the reflex function presides over the orifices and ter-
minations of the internal canals, such as the glottis and the sphincters, pre-
serving the former open, the latter closed ; and it maintains the due tone of
each muscle, and the due equilibrium of each system of muscles.

When excited, it gives origin to the movements observed in deglutition, or
vomiting, sneezing, tenesmus, &c. The fingers passed into the j)harynx of a
dog, through an incision made between the thyroid cartilage and the os

* M. Flourens seems clearly to have determined that sensation and volition are seated in the cere-
brum. Legallois (CEuvres, p. 17.) and he have ascertained that one office of the cerebellum is to regu-
late the voluntary motions. Legallois and Sir Charles Bell have shown that the medulla oblongata*
is the source of the respiratory motions. It is now, for the first time, I believe, shown that a peculiar
function of the medulla, superadded to its functions as a mere nervous chord, is that of imparting a
state of equilibrium to the muscular system, independently of the influence of the organs which origi-
nate and regulate the voluntary and respiratory motions. These several functions are separated, and,
in a certain degree, isolated, by removing the cerebrum, the cerebellum, and the medulla oblongata in
succession ; the last stage of the experiment leaves the reflex function alone, — a function which sup-
plies the deficiency left by the investigations of Legallois, M. Flourens, and Sir Charles Bell, and
constitutes the complement of the functions of the nervous system.

* lliis discovery of Legallois is amongst the most brilliant in physiology, and obviously presents
the nucleus of that, still more splendid, of the system of the respiratory nerves by Sir Charles Bell.
CEuvres, pp. 63, &c. ITie Nervous System, pp. 222, cxxv. &c.

ON THE MEDULLA OBLONGATA AND SPINALIS.

659

hyoides, excites the act of deglutition*; passed over the root of the tongue or
the fauces, it excites the associated actions of the muscles of the larynx and of
expiration-f-, which constitute the act of vomiting.

When morbidly augmented, it constitutes certain forms of disease, as tetanus,
hydrophobia, certain forms of tremor, paralysis agitans, chorea, stammering,
&c.; when diminished, it induces those forms of tremor observed when the vital
powers are enfeebled.

When otherwise morbid, it occasions other forms of disease, as the convul-
sion, the croup-like respiration, the affection of the sphincters, observed in
dentition, the various effects of intestinal irritation, &c.

The effects of the excited reflex function are sometimes observed in a part
near that irritated, as in the eyelids in winking, in the glottis on inhaling a
drop of water or particle of food, in the sphincter ani in dysentery, &c. ; some-
times in parts remote, as in the irritation of teething when this induces strabis-
mus, convulsion, the croup-like respiration, relaxed sphincters, &c.

However some of the facts detailed in this paper may have been previously
known, — and many were so known — they have never been accurately distin-
guished from sensation and volition, and associated with a peculiar reflex func-
tion of the medulla oblongata and medulla spinalis, influencing other organs
besides the limbs, and constituting the principle of tone and of a particular
series of actions. It has long been known, for example, that the limbs of a de-
capitated animal moved on being stimulated; but the phenomenon was con-
founded with sensation and voluntary motion. It has long been known that
carbonic acid could not be inhaled through the larynx ; but it has not been
shown that this phenomenon depends upon the presiding agency of the me-
dulla oblongata; nor has it been distinctly demonstrated that the functions of
the sphincter ani, by which the intestinal excretions are retained for a time, is
constantly dependent upon a similar agency of the lower part of the medulla
spinalis. In like manner, the facts relative to the irritability were altogether
known before Glisson and Haller finally separated this principle of motion

* De rUsage de I’Epiglotte, p. 3.

t See a Memoir by the author on the Mechanism of the Act of Vomiting, in the Journal of the
Royal Institution, 1828, Part L, (April to June,) p. 388.

X Compare Whttt, Legallois, Mayo, &c.

4 Q

MDCCCXXXIII.

660

DR. MARSHALL HALL ON THE REFLEX FUNCTION

from sensation and volition, with which, like the reflex function, it had pre-
viously been confounded.

An interesting parallel might, indeed, be instituted between the principle of
the reflex function and that of the irritability, in regard to their history and
degree of importance : their history is the same ; for both had been con-
founded with sensation and voluntary motion*: their importance is precisely
the same; for each presides over its own distinct order of functions.

Legallois plainly mistook the reflex fimetion of the medulla for the principle
of sensation and voluntary motion; and no physiologist has distinguished its
agency, in the function of the larynx and of the sphincters, from the influence
of the brain, or from irritability. The view of M. Cruveilhier, that the me-
dulla spinalis is a mere nervous chord, is at variance with all the facts and
experiments detailed in the course of tliis paper.

It is obviously from the mistake which has been pointed out, that Legallois
experienced the difficulty expressed in the following words : “ Comment se
fait-il qu’apr^s la decapitatian, les seuls mouvemens inspiratoires soient aneantis
et que les autres subsistent ? C’est la, a mon sens, un des grands myst^res des
puissances nerveuses, mystere qui sera devoile tot ou tard, et dont la decouverte
jettera la plus vive lumi^re sur le mechanisme des functions de cette merveil-
leuse puissance -J-.” It was impossible to explain this difficulty whilst the move-
ments of the excited reflex function were confounded with those of voluntary
motion ; but when this distinction is duly made, nothing is more easy. De-
capitation removes, in fact, the sources both of voluntary and of respiratory
motion ; both these kinds of motion consequently cease : but a class of motions
still remains, viz. those of the reflex function, attached to the remaining por-
tion of medulla. Thus is the veil raised from this apparent ^mystery’.

As Legallois has confounded the reflex function with the sensibility and
voluntary motions, M. Bracket^ has confounded it with the functions of the
ganglionic system, or the sympathetic. The latter physiologist concludes, that
whatever function remains after the division of the spinal marrow, in the organs
below that division, must be referrible to the influence of the ganglionic system.
In this manner he attempts to prove that some parts of the act and function

* Compare Whytt and Legallois. f GEuvres, pp. 63, 64.

J Du Systeme Nerveux Ganglionaire, p. 246, &c.

OF THE MEDULLA OBLONGATA AND SPINALIS.

661

of generation, in both sexes, besides the secretions, depend upon this influence ;
whereas it is certain that they depend upon the lower portion of the medulla
spinalis and belong to the reflex function. It is obvious, that, whilst the secre-
tions may depend on the ganglionic system, the act of excretion, and especially
the action of the ejaculatory muscles, is an excited act of the reflex function,
which has been fully proved to subsist in every portion of the divided medulla
spinalis. This view of the subject is greatly confirmed by a comparison of the
act alluded to, with that of deglutition (p. 640, note), and others demonstrably
belonging to the reflex function. We know that some reptiles remain in coitu
after the head is removed. This is then an act of the reflex function alone. It
may take place without sensation, as in cases of disease of the medulla spinalis.

I may state, in conclusion, that all the functions of the muscular system which
remain after the sources of the motive influence of the voluntary and respira-
tory motions are removed, with the exception of those of the heart, and other
muscles which contract upon the principle of excited irritability, depend upon
the reflex function.

The principles of the movements in the animal economy, viewed in an ana-
tomical and functional point of light, may now be enumerated thus :

] . The cerebrum, or the source of the voluntary motions.

2. The medulla oblongata, or the source of the respiratory motions.

3. The medulla spinalis generally, the middle arc of the reflex function.

4. The nervo-muscular fibre, or the seat of the irritabilitj'.

5. The sympathetic, or the source of nutrition, of the secretions, &c.

It is not pretended that this arrangement is either strictly accurate or com-
plete. These principles of action are, besides, frequently and variously com-
bined, and much ulterior investigation is required to ascertain the share and
fix the limit of each in various compound operations of the animal economy.

The reflex function of the different portions of the medulla presides over their
corresponding organs : the medulla oblongata presides over the larynx and the
pharynx ; the lumbar and sacral portion of the medulla spinalis presides over
the sphincter ani, the cervix vesicee ; and the intervening portions of the me-
dulla give tone and equilibrium to the corresponding portions of the muscular
system, and what Legallois has so vaguely designated “ to the corre-
sponding regions of the body. But the operation of the reflex function is by

4 Q 2

662

DR. xMARSHALL HALL ON THE REFLEX FUNCTION

no means confined to parts corresponding to distinct portions of the medulla.
Tlie irritation of a given part may, on the contrary, induce contraction in a part
very remote : the irritation of teething may induce spasmodic action or relax-
ation of the sphincters : the irritation of the nostrils, in the case of a young
liedgehog, when so languid that voluntary motion and respiration had ceased,
induced as energetic contraction of the most distant part of the panniculus
carnosus and of the muscles of the posterior extremities, as irritation of the
posterior extremities or tail themselves.

It would seem, from what I have observed in the young of the hedgehog and
of other animals, when languid, torpid, or dying, that the voluntary motions
cease first, then the respiratory motions, next those of the excited retlex func-
tion, and, lastly, those of the irritability; the last act of the irritability being
that which induces the cadaveric rigidity. After all evidence of irritability has
ceased, it is probable that the functions of the sympathetic may still continue.

Such is the order, then, in which this series of functions disappear in death ;
an order which is inverted when the same functions and their appropriate
organs gradually came into existence, in the foetal and natal states, and in tlie
progressive series of the animal kingdom. The movements of the foetus in
utero, are entirely phenomena of the reflex function : they occur in the anen-
cephalous as well as in the perfect foetus*. This function and the irritability
constitute, indeed, the principles of life and motion in the fatal state.

The functions, in sleep, seem to be diminished, and that in the same order.
This is particularly seen in the deep lethargy of the hedgehog. The animal
becomes quiescent ; then it nearly ceases to respire ; then the action of the pan-
niculus carnosus yields to partial relaxation ; lastly, the heart beats with a reptile
slowness. In ordinary sleep, the muscles which retain the eye 0})en lose their
powers, and the eyelids close by an act of the reflex function, just as they are
kept closed in the anencephalous infimt. The eye is only partially closed,
even during sleep, in cases of extreme languor and exhaustion, with diminished
energy of the reflex function. Volition is first impaired, and the eyelids close ;
the reflex function next fails, and the eyelids close partially only.

It appears probable that the facts of this paper may lead to some important
additions to our knowledge of anatomy, by inducing an accurate inquiry into
* See M. Lallemand’s Observations Pathologiques, p. 68.

OF THE MEDULLA OBLONGATA AND SPINALIS.

663

the origin, course, connexion, and distribution of the subcutaneous, or sub-
mucous, and muscular nerves, which constitute the arcs of the reflex function.
There can be no doubt that a system of nerves takes its origin from the
lower portion of the spinal marrow, to supply the sphincters and the organs of
generation, which may be compared to those which concentre in the medulla
oblongata. The medulla is also, in its whole course, the source of nerves which
supply the limbs, the tail, and the panniculus carnosus, in those animals which
possess these structures respectively.

It was observed in one frog that the strychnine applied to a single posterior
extremity induced general tetanus. General tetanus, in the human subject, is
the effect of the local wound of a nerve. These facts demonstrate the strict
connexion and unity of the different parts of the nervous system.

The anatomy of the reflex function must be particularly studied in the me-
dulla oblongata ; in the portions of the spinal marrow which give origin to
the nerves of the anterior and posterior extremities ; in that of the intermediate
space which supplies the trunk ; in that which is the source of the nerves of
the sphincters, the ejaculators, &c., and in that which supplies the tail ; and,
lastly, in reference to the several columns of which the spinal marrow is com-
posed. I think the investigation of the anatomy will, for various reasons, be
best pursued in the hedgehog.

It is gratifying to me to state that no part of these experiments has inflicted
pain, beyond that of prompt decapitation, or division of the spinal marrow.
This is true, at least, if the conclusion be correct, that when the head is re-
moved from the body, sensation and volition cease, whilst the reflex function
and the irritability alone continue; and it may be satisfactory to the humane
to know that the motions of the eel, for example, after the head is removed,
are not motions arising from sensibility, but from another principle, as distinct
from feeling as the irritability of the mere nervo-muscular fibre. This fact will
suggest the propriety, as well as the means of avoiding such monstrous cruelty
as that of skinning eels alive. This will be effectually done by first removing
the head, hov/ever the animal may afterwards move on the application of sti-
muli, and appear to feel.

664

DR. MARSHALL HALL ON THE REFLEX FUNCTION

V, Recapitulation.

To avoid misapprehension, I think it right, in conclusion, very briefly to re-
capitulate the claims of this paper :

1. Many of the facts which depend upon the reflex function have long been
known to physiologists :

2. But these facts only extend to the excited action of the reflex function,
seen in the limbs, and even they have been erroneously ascribed to sensation
and volition, or instinct :

3. The facts of excited movements of the larynx, pharynx, sphincters, and
ejaculators, and of the panniculus carnosus, have not been shown to be allied
to these, and to be dependent on the same individual function of the nervous
system :

4. It has not been shown that this function, in its natural state, constitutes
the principle of equilibrium and tone, in the whole muscular system, and the
principle which presides over the orifices and sphincters of the internal canals:

5. And certainly not, that this principle, morbidly affected, constitutes, in
its different forms, the diseases arising from dentition, and the diseases termetl
tetanus, hydrophobia, chorea, paralysis agitans, certain forms of epilepsy,
of tremor, of asthma, &c. &c. :

6. Nor that the same individual function is augmented or diminished to a
fatal degree, by certain poisons.

7. This series of facts has not been duly associated and shown to belong to
one particular order :

8. The principle of action in this order of facts has not been demonstrated
to be at once excited, and reffex, in its operations, to be essentially connected
with corresponding portions of the medulla oblongata and medulla spinalis,
and to be independent of the brain :

9. Nor has it been clearly distinguished from the other sources and princi-
ples of muscular motion existing in the animal economy, viz. volition, the
motive influence of respiration, and irritability, or shown to constitute, with the
irritability, the principle of life in the foetal state :

10. The reflex function appears, in a word, to be the complement of the
functions of the nervous system hitherto known.

OF THE MEDULLA OBLONGATA AND SPINALIS.

665

I trust it will be found, from this brief recapitulation, that the foregoing
paper may have done some little service to physiological science. I consider
the subject as but sketched, — the investigation as but just begun. One part
of this inquiry is altogether untouched, — the influence of the mind and emo-
tions, and the corresponding parts of the nervous system, upon the organs
which are the subjects of the reflex function. The muscles of voluntary and
respiratory motion are alike under the influence of the reflex function ; and
the muscles over which this function more peculiarly presides are impressible
through volition and respiration : other muscles, which are especially attached
to the reflex function of the lower portion of the medulla spinalis (p. 661), are
apparently under the influence of the cerebellum*. Mental emotions modify
the reflex function ; they induce sickness, relax the sphincters ; they also ag-
gravate the diseases of this function, inducing the attacks of epilepsy, of the
croup-like convulsion, &c.

* See Serres, Anatomie Comparee du Cerveau, tome ii. p. 601, &c.

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